1. Field of the Invention
The present invention relates to the field of consumer used by the consumer to monitor a telephone line to be certain that the telephone line is operative. A telephone line is inoperative when it is either broken, out, shorted or unplugged. Oftentimes, an individual who may be waiting for an important incoming telephone call has no idea that the telephone line has become inoperative. Unless the individual tries to make a call and discovers that the telephone line is inoperative, there is no way for the individual to know of this.
The present invention relates to the field of monitoring and signalling circuitry and apparatus which can detect telephone line failure and further provide both visual and auditory warning signals to alert a user when the telephone line becomes inoperative.
2. Description of Prior Art
A co-pending patent application "Telephone Line Monitoring Circuit For Providing A Visual and Auditory Signal If the Telephone Line Becomes Inoperative" (Ser. No. 07/462,218) was filed on Jan. 9, 1990.
In general, line monitoring devices have been produced in the prior art. The following patents are representative of known telephone line monitoring devices:
1. U.S. Pat. No. 4,841,559 issued to Curtis on June 20, 1989 for "Telephone Network Interface Tester".
2. U.S. Pat. No. 4,513,176 issued to Fostveit on Apr. 23, 1985 for "Test Apparatus For Telephone Equipment".
3. U.S. Pat. No. 4,827,498 issued to Ross on May 2, 1989 for "Telephone Line And Instrument Tester".
4. U.S. Pat. No. 3,976,849 issued to Champan on Aug. 24, 1976 for "Telephone Wiring Tester".
5. U.S. Pat. No. 4,544,807 issued to Sers on Oct. 1, 1985 for "Fault Detector Test Instrument".
6. U.S. Pat. No. 3,951,248 issued to Feiner et al on Apr. 20, 1976 for "Telephone Line Visual Status Indication Circuit".
7. U.S. Pat. No. 4,002,861 issued to Putt on Jan. 11, 1977 for "Protector Module Test Set".
8. U.S. Pat. No. 4,373,120 issued to McDonald on Feb. 8, 1983 for "Line Test Termination Device".
9. U.S. Pat. No. 4,564,728 issued to Romano on Jan. 14, 1986 for "Apparatus For Testing A Telephone Line".
10. U.S. Pat. No. 4,588,862 issued to Grabowy on May 13, 1986 for "Visual Display Network Interface".
11. U.S. Pat. No. 4,600,810 issued to Feldman et al on Jul. 15, 1986 for "Telephone Line Tester".
U.S. Pat. No. 4,827,498 issued to Ross relates to a telephone line tester which has a standard modular plug that can plug into a standard telephone line. The circuit of the tester is responsive to the flow of current therethrough for providing an indication of the operation of the source related equipment and/or the telephone instrument. The device is not a continuous monitoring device and requires that the user unplug the telephone and insert this plug into the line in place of the telephone line and then do the testing.
U.S. Pat. No. 3,976,849 issued to Champan illustrates a telephone wiring tester designed to receive modular terminal plug 17 and to test line voltage. This device also is not a continuous monitoring device and is a test device which is used when the telephone is unplugged. The device is used to test and check for the presence of a minimum voltage of the correct polarity between the tip and ring line conductors of a telephone installation and also to check for the presence of a proper AC lamp voltage between the ground and the lamp lead on a modular jack type telephone installation.
U.S. Pat. No. 4,544,807 issued to Sers discloses a fault detector test instrument for detecting faults on telephone lines. The device provides an indication of the most common wiring faults such as grounds, foreign E.M.F., resistance across the lines, open circuits, etc.
U.S. Pat. No. 4,513,176 to Fostveit shows a test apparatus for telephone equipment. The device discloses a multiplicity of test circuits that the owner can use to test for a problem in the line.
U.S. Pat. No. 4,841,559 to Curtis discloses another telephone test line type device.
U.S. Pat. No. 3,951,248 to Feiner discloses a telephone visual indicating circuit to enable an installer to determine without actually physically going off the hook what the status of a telephone line is.
U.S. Pat. No. 4,002,861 issued to Putt discloses a modular plug-in telephone test set in a carrying case.
U.S. Pat. No. 4,373,120 to McDonald discloses a line test device used by the telephone company to test the telephone line. It provides a characteristic signature recognizable by the telephone central office when a continuity test is made on the subscriber line.
U.S. Pat. No. 4,564,728 to Romano discloses another embodiment of a telephone line tester. This tester is a simple device which uses a bipolar LED comprised of two parallel light emitting diodes which are arranged between terminals 15 and 16 in opposite polarity. The telephone line tester comprised of this bipolar LED has coupled thereto two wires which terminate in a modular plug. The plug is inserted into the telephone jack and if the telephone line is operating properly, one of the diodes will illuminate depending upon the polarity of the lines.
U.S. Pat. No. 4,588,862 to Grabowy is a visual display network interface for placement between incoming telephone network access lines to a structure and the user telephone equipment within the structure.
U.S. Pat. No. 4,600,810 to Feldman is another telephone line tester which determines whether or not there is adequate power in the signal when plugged into the telephone jack.
Most of the prior art testing apparatus does not provide continuous monitoring of the line and is instead an intermittent test apparatus which requires disconnecting the telephone and then testing the line. Continuous monitoring is important for the average consumer who does not know when his or her line may go dead. In addition, for a blind person, a visual signal is not adequate to warn when the line has gone dead and a supplemental audible signal is required. In addition, the telephone in the household may only be in one room and the person may not be looking at the telephone for an extended period of time. Therefore, an audible signal to warn of line failure is also important under normal circumstances in case the telephone is not in easy view of the person. In addition, for a deaf person, an audible signal is not adequate to warn when the line has gone dead and a supplemental visual signal is required.
Co-pending patent application "Telephone Line Monitoring Circuit For Providing A Visual and Auditory Signal If the Telephone Line Becomes Inoperative" (Ser. No. 07/462,218) filed on Jan. 9, 1990 discloses a telephone line monitoring circuit which continuously detects a telephone line and will provide both visual and auditory signal when the telephone line is inoperative. In addition, the present invention discloses a telephone line monitoring circuitry and apparatus which uses a delay means to provide a delay of about ten seconds from the telephone line becoming inoperative to producing the alarm signals to prevent false alarms that may occur from brief and legitimate changes in the telephone line. It further discloses the use of an operational-amplifier means operated at micro-power level to further conserve energy, and an opto-coupler, an oscillator and a transformer to provide complete isolation of the circuitry to prevent interference with the telephone network. It additionally discloses the use of a secondary power source to further provide a DC back up power when the circuitry and apparatus is energized by an AC power source.